A few of the technologies covered in articles within this issue underscore the wide range of transmission speeds that users currently require or anticipate requiring, and the cabling that supports those speeds. In one case, it's singlemode fiber deployed in data centers providing the throughput capability necessary for the 400-Gbit/sec speeds on the horizon ("Long-wavelength optical networking brings singlemode fiber into data centers," page 17). In another case, it's Category 5e twisted-pair cabling supporting the 2.5-Gbit/sec backhaul for wireless LANs ("Protocol and hardware testing for 2.5GBase-T and 5GBase-T," page 12).
2.5G and 400G exist at opposite ends of the spectrum in terms of transmission speeds. The IEEE 802.3bz standard specifying 2.5 and 5GBase-T is still new, having been finalized in September 2016. And the IEEE 802.3bs standard specifying 400-Gbit Ethernet isn't even "new" yet; it may publish at the end of this year. But it's noteworthy that the respective cabling technologies aimed at supporting these speeds have been around for a long while. Early iterations of Category 5e cabling (some of which ended up complying with the eventual standard ... right?) were installed into commercial office buildings in the late 1990s. And singlemode fiber ushered in the era of communication via fiber optics. Yet here both are today, each having stood the test of time in its own right, poised to be an enabling technology for a new protocol for data communication.
Both singlemode fiber and Category 5e cabling will have to prevail over other options. On the 400G landscape, singlemode faces competition from parallel-optic permutations of multimode fiber supporting short-wavelength optical transmission. Among them is short-wavelength division multiplexed (SWDM) technology that recently was specified by the SWDM Multi-Source Agreement Group. SWDM is not yet incorporated into an IEEE draft specification, but many expect it soon will be.
Category 5e faces a different challenge. Whereas alternatives to singlemode for 400G make an economic case for deployment, some skeptics of 2.5G over Category 5e say the just-about-20-year-old systems simply won't be up to the task. For those who plan to give it a try, test specifications exist to characterize the installed base.
How far into the future will decades-old technology take us? The answer to that question is yet to be revealed.
Patrick McLaughlin
Chief Editor
[email protected]